This invention concerns the design and construction of a rack-and-pinion telescopic lifting apparatus. The device can vertically displace a load over several meters. It consists of a telescopic pole whose base can be equipped as needed with a fixed or mobile stand and, at the top, with any system that will enable the load to be attached or handled.
Telescopic lifting devices already exist which comprise modules that slide vertically over each other and in which the movement of an upper module with respect to a lower module is obtained by one or several cables connecting up the modules. Extension of the system and vertical displacement of the load attached to the upper module are obtained by means of a tensile force exerted on the crank handle of a winch fixed to the outside of the lower module and the base of the device and to which the end of one of the cables is connected.
A winch-driven cable has the disadvantage of requiring a complex set of pulleys which generates a large amount of friction, requiring both additional effort on the part of the operator to lift the load and a much longer load lifting time. The cable is also exposed to a number of risks such as crushing, jamming and corrosion, which rapidly reduces its life time and requires costly regular maintenance operations. At the extreme, the cable can break and cause accidents.